Problem with sliding patio door

[mrs_overall]

Help!
I unlocked & opened the door as usual this morning but now I can't get it to close fully or lock. It's not on a runner so it can't have "dropped".
Any suggestions please?

[Lonnie]

Couldn't possibly one of the hinges has come slightly loose maybe?,

[Wak]

Our front door (white plastic) sometimes does this and it's always the inside doormat which moves forward and the corner gets trapped between the door and the door frame and won't let the door close properly, consequently, the locks and fasteners won't work as they should.
Check your doormat before calling in the workmen.

[Wak]

Sorry, just noticed that it's a patio door and not an ordinary front/back door.

[mrs_overall]

Ta anyway.
We can't fathom it out - a workman is coming to fix it